Process for stabilizing mineral oils



Oct. 13, 1936. B. H. SHOEMAKER ET AL 2,057,212

PROCESS FOR STABILIZING MINERAL OILS Filed Oct. 31, 1932 3 Sheets-Sheet1 'lacgirgg Tzifiw (101259) flouns 6 Tmpcmtara-Dggrws F Jn0entor.s:- FDermrdfthoamlwr MrzrzcthTzylor BYBMQI I ATTORNEY Oct. 13, 1936. B. H.SHOEMAKER Er AL 2,057,212

PROCESS FOR STABILIZING MINERAL OILS Filed Oct. 51, 1932 a sheets-sheet?Jczybolt kseaizda at 210??? 2 2 Q 100 1.50 Time infioara Z Jnvantorv:-Fiig fiermrdji .fifzoemakar JCarmat/z Tylor BMCZ- ATTORNEY True Color-PROCESS FOR STABILIZING MINERAL OILS Sheets-Sheet 3 Fi led Oct. 31, 1932o aa .200 .140

J2me inJtoans drbvantor F Demamlflflzoarrzaker Kenneth Taylor BY BMKZ.BM

ATTORNEY Patented Oct. 13, 1936 UNITED STATES PROCESS FOR. STABILIZINGMINERAL OILS Bernard H. Shoemaker, Hammond, Ind., and Kenneth Taylor,Chicago, Ill., assignors to Standard, Oil Company, Chicago, 111., acorporation of Indiana Application October 31, 1932, Serial No. 640,386

10 Claim.

This invention relatesto the stabilization of mineral oils and itpertains more particularly to a process and composition for preventingsludge and color formation in lubricating oils when used underconditions conducive to deterioration.

Mineral oils, and particularly lubricating oils, when used in internalcombustion engines or under conditions where the oil comes in contactwith hotsurfaces, deteriorate andform sludge,

P deteriorate in colonfcrm varnish-like products that deposit on thesurfaces being lubricated and the viscosity of the oil increases withuse. This deterioration of mineral oils is particularly noticeable withoils used to lubricate internal com- 3 bustion engines. The sludgeformed collects on the piston rings and causes them to stick. Also,sludge collects in the oil pumps and oil lines and greatly retards theflow of oil and in some cases plugs up the oil lines and small passages.

' The object of our invention is to provide a method for stabilizingmineral oils and particularly lubricating oils against deterioration.

Another object is to provide a method for inhibiting thesludge formationof mineral oils by i adding to the oil an inhibiting catalyst.

Another object is to prevent the increase in viscosity of the oil uponcontinued use.

Another object'is to provide a method for prenventing colordeterioration of the oils.

A further object is to provide a process for preventing the formation ofvarnish-like products in lubricating oils and the staining of the partsto be lubricated.

In internal combustion engines, it is very important that thelubricating oils be stable as to sludgeformation. We have found thatmotor oils have a great tendency to sludge and deteriorate at the highoperating temperatures generally encountered in internal combustionengines such as are used in automobiles and airplanes. At these hightemperatures it is common for lubricating oils to decompose and formsludge and coke on the pistons and in the ring grooves of the pistons.Thisresults in sticking of the rings which,

5 in turn,allows more oil to gain access to the cyl- 5 to note that arelativelysmall increase in temperature will greatly increase the rateof sludge formed. The sludge stability of the oil with reference totemperature, shown in Figure 1, was determined by heating a quantity ofoil to the desired temperature and bubbling air through the sample attherate of liters per hour. At intervals, 10 grams samples werewithdrawn and tested for sludge by the precipitation method described inAmerican Society of Testing Materials Proceedings, volume 24, page 967.

Another undesirable characteristic of lubricating oils is their increasein viscosity upon use. The curve shown in Figure-2 illustrates thisproperty of mineral oils. It will be observed that the Saybolt viscosityincreases greatly upon use. The results expressed by the curve in Figure2 were obtained by maintaining a Pennsylvania oil at 340 F. and bubblingpreheated air through the oil at the rate of 100 to 150 liters per hour.It is apparent that when mineral oils are used at elevatedtemperatures'in internal combustion engines, the viscosity increasesupon continued use and the oil will become so viscous that a heavy loadis put upon the engine, especially when starting. This is particularlynoticeable in cold weather.

Another common and undesirable property of mineral oils and particularlythose lubricating oils used in contact with hot surfaces, such as ininternal combustion e es. is the development of color. Curve A in Figure3 shows the rate of color formation when a heavy Mid-Continentlubricating oil is heated to 340 F. while air is bubbled into the oil atthe rate of 10 liters per hour. Curves B and C show the rate of colorformation in the same oil when a small amount of sodium butylate andpotassium butylate, re spectively, are dissolved in the oil. It isapparent from the curves that a small amount of these alkalinealcoholates are very effective for retarding color formation.

We have found that mineral oils, and particularly lubricating oils, canbe stabilized against deterioration as illustrated by sludge formation,increase in viscosity upon use, staining of the surfaces to belubricated and color formation, by adding to the oil a small quantity ofan alkaline alcoholate or mixture of alkaline alcoholates. We have foundthat the alkali metal alcoholates and alkaline earth metal alcoholates,as well as the thio alcoholates, are particularly suitable forstabilizing mineral oils in this respect. The compounds used forstabilizing these oils have the following general formula:

wherein x-is a mono-valent alkaline metal and x1 is a di-valent alkalinemetal, 13 represents an oxygen or sulfur atom and R. represents analkyl,

cyclo-alkyl or aralhl radical or derivatives.

thereof. We may use the aliphatic alcoholates,

cyclic alcoh'oiates aralkyl alcoholates, examalcohols such as cyclohexanol, cyclo butanol,

hydro phenols, cyclo hexyl mercaptan and the like; secondary andtertiary aralkyl alcohols such as benzyl alcohol, phenyl ethyl alcohol,dibenzyl alcohol, tolyl alcohols and thelike;

also the alkaline metal derivatives of organic compounds capable offorming the enolic structure, such as acetoacetic ester and ketones, areeiiective for stabilizing mineral oils. The tautomeric forms ofacetoacetic ester are:

on I cnlc=cncooclm cur -c l cmcooclm The alkaline metal eel-mum or theenolic tautomer of the above esters and other compounds such as ketonescontain the following characteristicgroup:

wherein R represents an alkalimetal.

' 'Ihe stabilized oils are prepared by dissolving a small amount of thealcoholates therein. The preferred amounts range from 0.1 to 0.5%, the

amount varying with specific materials. Howdesired.

ever, larger amounts up to 1% may beused if ;The followingtable'illustrates the results obtained with a heavy Mid-Continentlubricating oil, having an original true color of 21, when stabilizedwith alkaline alcoholatesat a tempera- .ture of 320 F. V 7

Table 1 Tnm Ior Sludglng Example Btabilizar Percent m a 5 (hours) hourshours 10 1 Control 1435 am an 2 (4H|0Na.- 0. I 248 87 3 041100 0.2 1% m30 v 4v 0.4 m in 5 0.2 12 7B0 l 6 0.8 116 151 41 7 0.3 IN 478 41 8 0.4 m12:0 9 .03 mo 10 0.8 82 111 42 ii 0.2 flit U5 as 12 Namethyl ethylhclone--. 0.2 100 30 13 Na-mothyi ethyl vire 0.8 to 82 44 14 0.3 84 7041 15 Nil-bitty (tort)- 0.2 an 1055 i0 nty 0.3 l3l 210 45 i7Na-decylato. 0.4 675 18 Na-triothylena glycol: 0.3 516 lh-om the abovetable it is apparent that the alcoholates of alkaline metals 'are veryeii'ective for preserving color and retarding sludge formation inlubricating oils. It shouidbe noted that formation in lubricating oils.

gained very little in color. Curves C and B in Figure 3 further show theextent of color stabilization 'over longer periods of time. It will beobserved that'after-100hours, the color of the oil issubstantially'one-third the color of the unstabilized oil. It should befurther noted that V the alkaline-alcoholates derived from the lowmolecular weight metaissuch as lithium and sodium, and the highmolecular weightalcohols such as butyl amyl and cyclo heal alcohols, areparticularly eflective for stabilizing the oils against sludgeformation.

The following table further shows the effectiveness of the alcoholatesfor inhibiting sludge The particular oil used was v a heavyMid-Continent lubricating oil which hadbeen treated with 2 lbs.- ofsulphuric acid per gallon of oil.

Table 11' V Sludge time in horns rcorm oi slud g l:

Control 02 NaOGJI- m5 0 o K0011!- 18 We have found it particularlydesirable to add small quantities of an alcoholate to oils for seasonalstorage to inhibit color and sludge formation. "As indicated by theabove tables, it is apparent that the alcoholates are very eifective forinhibiting the deterioration of the oil.

As pointed out hereinbefore in connection with Figure 2, the viscosityoi the oil greatly increases as the oilis used and we find thatvthepresence of a small amount of alcoholatas will retard this increase inviscosity upon use.

The term "stabllim" is used in our application in a generic sense toinclude the of the oil against deterioration in any of the foregoingrespects, such as sludge formation, color formation, increaseinviscosity and the formation of varnish-like products. The alkalinecompounds ;used in our invention are not reducing agents and theirstabilizing action cannot be explained by the theory upon which theaction of antioxidants is explained. However, it isthought that thedeterioration oi. mineral oils is accompaniedvby the formation ofintermediate acidic products, and the alkaline derivatives of compoundscontaining the alcoholate structure retard the formation of theseintermediate acidic products and thereby stabilize the mineral oilsagainst deterioration. Our invention is not limited to the specificalcoholats disclosed above, but it includes the, alkaline metalderivatives of other reference to certain oils and compounds, the scopeof our invention is not limited thereby except insofar as set forth inthe claims.

We claim:

1. A sludge-resistant mineral lubricating 011 comprising a viscoushydrocarbon lubricating oil and from 0.1 to 0.5% of an alkalimetalalcoholate having the following formula:

X-BR wherein X represents a mono-valent alkali metal, B represents anoxygen or sulfur atom, and R represents an alkyl, cyclo-alkyl, oraralkyl radical.

2. A sludge-resistant mineral lubricating oil comprising a viscoushydrocarbon mineral oil and a small proportion of an oil-solublealkaline metal alcoholate.

3. A sludge-resistant mineral lubricating oil comprising a viscoushydrocarbon mineral oil and from 0.1 to 0.5% of an alkali metalalcoholate dispersed therein, said alcoholate having the followingformula: V

XBR

wherein X represents a mono-valent alkali metal, B represents an oxygenatom, and R represents an alkyl radical containing at least 3 carbonatoms, a eyclo-alkyl or aralkyl radical.

4. A sludge-resistant mineral lubricating oil comprising a viscoushydrocarbon mineral oil and from 0.1 to 0.5% of an oil-soluble alkalimetal alcoholate having the general formula:

wherein X represents a sodium atom, B represents an oxygen atom, and Rrepresents an alkyl radical containing at least 4 carbon atoms.

5. A sludge-resistant mineral lubricating oil comprising a viscoushydrocarbon mineral oil and a small proportion of an oil-soluble alkalialcoholate selected from the group consisting of sodium propylates,sodium butylates, potassium butylates, sodium amylates, potassiumamylates,

lithium butylates, and the sodium derivatives of butyl mercaptan.

6. A sludge-resistant mineral lubricating oil comprising a viscousmineral oil and from 0.1 to 0.5% of an alkali metal alcoholate selectedfrom the group consisting 01' sodium propylate, sodium butyiate,potassium butyiate, sodium amylate, and potassium amylate.

'7. A sludge-resistant hydrocarbon lubricating oil comprising a viscoushydrocarbon mineral oil and a small proportion of an alkali metalalcoholate selected from the group consisting of sodium propylate,sodium butyiate, potassium butyiate, sodium amylate, potassium amylate,lithium butyiate, and sodium derivatives of butyl mercaptan.

8. A sludge-resistant mineral lubricating oil comprising a viscoushydrocarbon mineral oil and a small proportion of an oil-soluble alkalimetal derivative of the enolic form of an aliphatic ketone.

9. A sludge-resistant mineral lubricating oil comprising a viscoushydrocarbon mineral oil and a small proportion of an oil-soluble alkalimetal derivative of the enolic form of an aliphatic ketone, said alkalimetal derivative containing the following group wherein R represents analkali metal.

10. A sludge-resistant lubricating oil comprising a viscous mineral oilhaving incorporated therein a small proportion of an oil-solublealkaline alcoholate of the following formula:

wherein X1 represents a divalent alkaline metal, B

represents an oxygen or sulfur atom, and R represents an alkyl,cycle-alkyl or aralkyl radical.

BERNARD H. SHOEMAKER. KENNETH TAYLOR.

